A 53-year-old teacher was fatally shot on Monday in San Bernardino, California, when her estranged husband stormed into her classroom and opened fire. An 8-year-old boy who was struck by gunfire also died later and another 9-year-old student was wounded in the shooting and was in stable condition, according to NBC News. After killing his wife, police said, the gunman fatally shot himself.

Karen Smith was a special needs teacher at North Park School, where she was teaching a class of 15 students on Monday morning. At about 10:30 a.m., authorities said, her husband, Cedric Anderson, walked into the school carrying a concealed weapon and, upon entering the classroom, abruptly began shooting. Police say he fired six rounds and then reloaded his weapon before the rampage was over. After Anderson killed himself, police said, investigators found a .357 revolver lying on the floor next to his body.

Smith and Anderson were newlyweds — they married in January — but had quickly become estranged, according to The Los Angeles Times, which spoke with Smith’s mother, Irma Sykes. “She thought she had a wonderful husband, but she found out he was not wonderful at all,” said Smith’s mother, Irma Sykes. “He had other motives. She left him and that’s where the trouble began.”

Though Sykes declined to go into great detail about what prompted her daughter to seek a divorce from Anderson, police revealed that Anderson had a criminal history that included allegations of domestic violence. Anderson, also 53 years old, posted a series of videos on Facebook just after the pair were married that depicted the couple as being in love and happy. But posts Anderson made on other topics provided a window into the rage seething beneath the surface. According to the L.A. Times, Anderson had been previously married, had a son and had served in the U.S. Navy for eight years. He was also a local pastor and described as a “deeply religious man.”

Smith has four children, all of them adults now, and began her teaching career later in life, just a decade ago. She followed in the footsteps of her mother who was a teacher for 41 years. Family members and friends remembered her as a “hero” in and out of the classroom.

Sykes, Smith’s mother, grieved and referring to Anderson’s faith, said, “He killed her, and he killed himself. And I want to see what he’s going to say to God about that.”

On Tuesday, Gabby Giffords, the former U.S. congresswoman from Arizona who survived a 2011 shooting rampage after being shot in the head and has become an advocate for gun control, spoke out about the tragedy, calling it “unimaginable.”

“My heart is breaking for San Bernardino, which like so many communities around the country has mourned far too many innocent lives because a violent person was able to get their hands on a gun,” Giffords said in a statement, referring to the 2015 terror attack that claimed 14 lives in the city. “We can no longer call events like this ‘unimaginable,’ because they happen with alarming frequency. It’s time that all Americans have the courage to truly fight this crisis by standing up and demanding the smart gun laws we know save lives.”